1. Field of the Invention
The present invention relates to the set-up of computer system mother boards to accommodate different configurations of components. More particularly, it relates to a key activated switch matrix on a mother board that enables a dedicated key when inserted to select a subset of selectable parameters and thereby configure the mother board without further operator intervention.
2. Description of the Prior Art
Personal computer architectures are organized around one or more system busses to which are connected a CPU, high speed system memory, a display, high capacity memory and a host of peripheral devices such as printers, modems, sound cards, CDROMs and the like. The system busses along with the CPU and system memory and some peripheral devices are usually mounted on a system printed circuit board, often called a mother board.
The components mounted on the mother board come in many varieties. For example, a typical CPU may be labeled at the factory as operating at 120 megahertz, but this same CPU can be operated in a system at several other frequencies such as 100, 90, 75 and even 150 megahertz. Typically, the frequencies at which a system operates are determined by a single quartz controlled clock mounted on the mother board which provides the clock signals for the system busses and all components of the computer system.
To keep the costs of computer systems low, there are only a few mother board designs and each design supports a wide variety of computer system configurations. For in addition to computer speeds, there are several bus speeds and several CPU core voltages that must be accommodated. In order to do this efficiently, mother board designers have developed single board designs that can be switched between several different configurations. For example, a single mother board design can support a CPU with speeds of 120, 90 and 75 megahertz and with CPU core voltage levels of 5, 3.54, 3.36 and 2.5 volts. This means that for each mother board, their is a set of selectable parameters. The mother board designs contain a matrix of individual switches that are set by hand to select a specific subset of parameters from the set of selectable parameters.
In the prior art, the switches are either dip switches or suit case jumpers. In either case a technician must set each individual switch, one at a time. And often the number of switches to be set is quite large. Usually, the technician will use a switch map to guide them in the setting process.
There are two problems with the foregoing process. First, many mistakes are made. The technician must be precisely correct in order for the configuration to be right. This is difficult to do when dealing with very large numbers of mother boards. Also, configurations are often changed during the manufacturing and test process. For example, the automatic test equipment that tests the CPU after it has been mounted on a mother board typically perform their tests at one frequency, say 90 megahertz. Thus, all switches would be set for 90 megahertz operation for test purposes. However, after the test is complete the mother board would have its configuration switches reset for the shippable configuration. In this process many mistakes are made.
Secondly, with conventional dip switches or suit case jumpers, any person can, with modest computer skills, reset the configuration switches and thereby reconfigure their computer. This creates a host of problems for computer system manufacturers. For example, an end user could reconfigure a mother board to run a CPU designed to run at 90 megahertz at 120 megahertz. The system would probably run; however, the life expectancy of the CPU would go down substantially and would therefore increase the service expenses of the manufacturer.